Polyolefin resins such as polyethylene and polypropylene are the most popular plastics that are widely used for daily necessaries, toys, machine parts, electric and electronic parts, and automobile parts. The recent requirement increasing in the art is for gas-barrier (transmission-resistant) resin articles capable of preventing the contents from leaking out and protecting them from the open air for ensuring the safety and the storage stability of the contents and for protecting the environment from pollution. However, since polyolefin resins are poorly resistant to liquid chemical and vapor transmission through them, their use is often limited, and it is desired to improve them.
For improving for the physical properties of such polyolefin resins, resin compositions and moldings consisting of polyolefin resin and polyamide resin of good transmission resistance have heretofore been proposed in the art. The method could improve the transmission resistance of the resin compositions and moldings over that of moldings of polyolefin resin alone, but is still unsatisfactory. Therefore desired is a technique of further improving the transmission resistance of polyolefin resin structures.
For fuel tanks and oil tanks for automobiles, converting metallic containers into plastic containers is now actively investigated, as plastics are lightweight and easy to mold and work, their design latitude is broad, and they are easy to handle. The matter of importance with such plastic containers is that they do not leak the contents and can protect the contents from the open air for ensuring the safety and the storage stability of the contents and for protecting the environment from pollution. Polyethylene, polypropylene and other polyolefin containers are the most popular plastic containers, but their barrier properties against gasoline and other specific oils are unsatisfactory. Therefore, it is difficult to directly use them for fuel tanks and oil tanks for automobiles. For such use, in general, they are worked into multi-layer structures by coating them with a barrier layer of resin of high transmission resistance.
One typical example of the resin to form such a barrier layer is polyamide resin (for example, as in JP-A 220738/1983). However, the recent tendency in the field of automobile fuel is being toward using a mixture of gasoline and alcohol, gasohol, for which the plastic containers obtainable in the above-mentioned prior art are unsatisfactory in point of their barrier properties. Therefore desired is a technique of further improving the barrier properties of plastic containers.
On the other hand, it is known that PPS resin has extremely good barrier properties against liquid chemicals such as gasoline and automobile oil, and against water and carbon dioxide. Blow-molded containers and tubular structures of such PPS resin (for example, as in JP-A 90216/1987, 255832/1986, 32816/1991), and multi-layer structures with a barrier layer formed of a specific PPS resin and a modified polyolefin (for example, as in JP-A 190980/1994) have been proposed. However, since its interlayer adhesiveness to other resin is poor, PPS resin has some problems in that its coextrusion and lamination with other resin materials such as polyethylene, polypropylene and other polyolefins is difficult and its main component must be an expensive specific PPS resin. For these reasons, the application range of PPS resin is limited.
The present invention is to improve the transmission resistance of polyolefin resin, and its object is to provide resin structures of specifically improved liquid chemical and vapor transmission resistance, not detracting from the properties such as toughness, moldability and workability intrinsic to polyolefin resin, especially to provide polyolefin-PPS resin structures favorable for vapor and/or liquid barrier articles, and to provide multi-layer structures of good transmission resistance, moldability, workability, interlayer adhesiveness and toughness that are favorable to plastic containers and can be stably and economically formed into good plastic containers.